Marksmen from Britain's Metropolitan police laid siege to the house in Markham Square in the affluent area of Chelsea for four hours after reports of a man firing shots in a house there shortly before 5 pm.
Armed police exchanged gunfire several times with the man who later died, a police spokesman said on condition of anonymity in line with force policy.
The spokesman said he could not say whether the man was shot dead by officers because an investigation was being opened by Britain's police watchdog, the Independent Police Complaints Commission.
